Detailed morphological studies of renal diseases including electron microscopy and immunofluorescence microscopy will be continued and correlated with clinical and physiological changes. The proposed studies for the forthcoming year include mesangiocapillary glomerulonephritis, primary and secondary amyloidosis and systemic lupus erythematosus. In addition, the types and nature of lesions in heroin addicts will be examined in detail; some of these lesions appear to be toxic in nature and others immunologic, possibly related to repeated infections. The renal lesions associated with necrotizing angiitis will be reviewed. Likewise, a study will be undertaken of glomerular lesions in chronic transplant rejection. The relation of so-called sarcomatoid mesothelioma to the epithelial mesothelioma will be studied by light and electron microscopy in order to establish the histogenesis of cell types. Also rare forms of diffuse mesothelioma which have a very slow course, will be characterized by light and electron microscopy and histochemical means. Study of radiation effect upon the testis will be continued using doses between 100 and 500 rads.